Filter device

ABSTRACT

The invention relates to a filter device comprising at least one filter housing ( 1 ) in which at least one filter element ( 21 ) is arranged. Inside the filter housing ( 1 ), the filter element separates a clean side ( 9 ) from an untreated side ( 13 ). The device is characterised in that, on the clean side ( 9 ) of the respective filter housing ( 1 ) at least one storage unit ( 3 ) having at least one movable separating element ( 47 ) is connected, which divides the storage unit ( 3 ) into two working chambers ( 49 ) or pressure chambers ( 43 ).

The invention relates to a filter device comprising at least one filter housing in which at least one filter element is disposed that separates the clean side from the untreated side inside the filter housing.

Filter devices of this kind are used in a great number of the most varied applications as well as in the filtration of different fluids, wherein different constructions of the device are possible, depending on the area of application. Among the preferred applications is the purification of fluids, lubricants or fuels. Similarly, such devices can be used for water purification, or in connection with different kinds of process or operating fluids.

Irrespective of varying constructions and the great variability applications, as a common requirement, all of these filter devices must be able to ensure the uninterrupted operation of the connected system that is to be supplied with the filtrate.

In view of this problem, it is the underlying object of the present invention to provide a filter device with operational properties that are especially suited to meet these requirements.

According to the invention, this object is achieved by a filter device with all of the characteristics as set forth in Claim 1.

Correspondingly, an essential special aspect of the invention provides that at least one storage unit is connected on the clean side of the respective filter housing that includes a separating element, which is movable between two working or pressure chambers. This way, it is possible to easily support the operation of the device by a pressure control that influences the pressure level on the clean side inside the filter housing providing an adjustment to the respective operating state. For example, during normal filtration operation, it is possible to compensate for pressure variations due to volume changes in the space of the storage unit that is connected to the filter housing (pulsation dampening), such that fluctuations of the volume flow of the discharged filtrate are avoided. Similarly, if necessary, the filtration process can be supported by a suction effect of the storage unit. In filter devices that are provided with a backwashing means, it is advantageously possible to avoid a drop in the volume flow of the filtrate due to volume compensation by the storage unit, as would be caused to occur with the start of a backwashing process by a secondary flow of the backwashing volume, and/or to support the backwashing means by applying pressure to the clean side of the device.

DE 199 56 859 A 1 discloses a backwashing filter device that, during backwashing processes, discharges a backwashing volume of fluid from the filter housing and that can be connected to a negative pressure means, and said negative pressure means can be activated to generate negative pressure at a respective filter element that is to be backwashed. The negative pressure means includes a suction pump that is constructed in the manner of a diaphragm accumulator having a diaphragm that can be deflected for pumping motions by means of a mechanic drive. Although it is possible with the known solution to increase the intensity of the backwashing operation, the increase of the backwashing volume, however, that is generated by the suction action, results in an increased drop in the volume flow of the filtrate due to secondary flow.

In especially advantageous embodiments of the invention, the arrangement is such that the space of the storage unit, which is separated by the separating element from the fluid chamber that is connected to the clean side of the filter housing, constitutes a working chamber that can be connected to a source for a pressure medium. By a corresponding application of pressure to the working chamber, it is possible to control the operating state of the storage unit, and therefore the influence thereof on the filtration or backwashing operation. Particularly advantageously, it is possible to provide a hydro-pneumatic pressure accumulator as a storage unit having a working chamber that can be connected to a pressure source, particularly a compressed air source.

In especially preferred embodiments, a pressure accumulator is provided in the form of a piston accumulator.

If the filter device according to the invention is configured as a backwashing device, the arrangement can be especially advantageously designed such that the filter housing constitutes a cylindrical internal chamber that has filter cartridges that can accommodate through-flow in both directions for filtration or backwashing operations, wherein at least one filter element is backwashed by means of a backwashing device for cleaning the effective filter surface while, simultaneously, the other filter elements accommodate flow-through from the outside to the inside for the purpose of the filtration, such that the internal chamber of the filter housing surrounding the filter elements constitutes the clean side that is connected to the fluid chamber of the pressure accumulator.

In backwashing filter devices of this kind, it is possible for the internal chamber of the filter housing to be open at the top end thereof transitioning into the cylinder chamber of the piston accumulator that is provided as pressure accumulator, which is disposed coaxially relative to the vertical axis on the filter housing and constitutes the fluid side. Aside from the advantage of the especially compact construction, the further advantage is that the operation of the storage unit is not associated with any losses in flow because the filter housing immediately transitions into the fluid chamber of the pressure accumulator.

In especially preferred embodiments, the opening of the upper end of the internal chamber of the filter housing extends over the entire inside diameter thereof, wherein the diameter of the immediately following cylinder chamber of the piston accumulator has at least the size of the diameter of the internal chamber of the filter housing. The transition of the filter housing into the piston accumulator is therefore virtually step-free.

It is especially advantageous for the arrangement to be provided such that the cylinder jacket of the piston accumulator crosses over the open top end of the filter housing, has an internal thread and is screwed together with the external thread of the filter housing. Correspondingly, the housing and piston accumulator form an especially compact structural unit.

Regarding the operating behavior, particularly during the backwashing operation, the largest value of the volume of the fluid side of the pressure accumulator is preferably equal to or greater than the volume of the internal chamber of the filter housing surrounding the filter elements. A sufficiently large volume of the filtrate is therefore available in the storage unit to compensate the volume flow of the backwashing quantity to thereby maintain a constant volume flow of the discharged filtrate during a backwashing process.

The arrangement regarding the backwashing means can be selected such that the same includes a backwashing valve in the backwashing line, which is connected to the untreated side of the filter element that is to be backwashed, and that can be opened for backwashing processes, wherein a valve means is connected to the working chamber of the pressure accumulator that can be triggered as a function of time and actuation of the backwashing valve to supply compressed air into the working chamber or discharge compressed air from the working chamber of the pressure accumulator.

In a preferred embodiment of the construction of the filter device, the filter elements are disposed sequentially having the ability to pivot around the vertical axis, which is achieved by a pivot means that includes a rotary drive, from their filtration position into a backwashing position that is aligned with the backwashing line, and back to the filtration position.

The filter elements can be provided in the form of tapered slotted screen tube elements.

Below, the invention will be described in further detail based on an embodiment that is depicted in the drawing.

Shown are as follows:

FIG. 1 is a symbolic diagram of the hydraulic circuit of an embodiment of the filter device according to the invention in the form of a backwashing filter device; and

FIG. 2 is a longitudinal section of a filter housing and the associated storage unit of the embodiment.

The filter device according to the invention will be explained in further detail using the example of a backwashing filter device. The device comprises a filter housing, designated overall in FIG. 2 by the numeral 1, as well as a storage unit that is a piston accumulator 3 in the depicted embodiment. The filter housing 1 is designed in two parts and includes a housing bottom part 5 and a housing top part 7 that are screwed together forming a seal. The hollow-cylindrical housing top part 7 defines, in conjunction with the housing bottom part 5, an internal housing chamber 9 in the shape of a hollow cylinder that is open at the top end 11 thereof.

The housing bottom part 5 and a pivot means 23 fastened thereto correspond in terms of their construction substantially to the related components in a backwashing device as disclosed in DE 10 2004 004 756 A1, which means there is presently no need to discuss the entirety of the constructive details of the housing bottom part 5 and of the pivot means 23. As in this solution that is provided by the prior art, the bottom part 5 includes an inlet 13 for the fluid that is to be filtered as well as an outlet 15 for the filtered fluid. Located diametrically opposite of the vertical axis 17 relative to the inlet 13, a backwashing outlet 19 is disposed within the housing bottom part 5, by which the backwashing fluid volume can be discharged from the device.

Tapered filter elements 21 are inserted inside the filter housing 1, wherein it is possible to use at least in part cylindrical filter elements (not shown) instead of the tapered filter elements 21. The mentioned tapered filter elements 21 can be slotted screen tubes that are disposed in groups around the vertical axis 17 at relative distances to each other along the circular arch within the filter housing 1. In one embodied example that is not shown in further detail, the filter elements 21 can also be disposed, divided in groups, along multiple cylindrical arches of the filter elements 21. However, in the embodied example as shown in FIG. 2, a total of four filter elements 21 are disposed, seen from a perspective relative to the vertical axis 17, diametrically opposite each other. Seen from the perspective of FIG. 2, the filter element 21 that is visible on the right side therein is shown in the backwashing position thereof, while the other filter elements 21 are in the filtration position.

As in the known solution (DE 10 2004 004 756 A1) that was mentioned previously, the individual filter elements 21 can be sequentially moved by the pivot means, designated as a whole with the numeral 23, from the filtration position thereof into the backwashing position and back into the filtration position, wherein the rotational movement for the individual filter elements 21 can be clockwise or counterclockwise. The pivot means 23 includes a drive motor 25 (hydraulic or electric) that generates a controlled stepwise rotary movement of a shaft 27 powered by a drive 29 that is connected to the filter support 31. Said filter support is guided, rotatably and sealed, by the circular circumference thereof via a sealing apparatus 33 and along the internal wall of the bottom part of the housing 5.

The filter elements 21 are disposed such on the filter support 31 that the internal filter cavity is aligned with the openings 35 in the filter support 31. One of these openings 35 of the filter support 31, respectively, can be aligned with a backwashing opening 37, as demonstrated in FIG. 2 in an exemplary manner by the filter element 21 seen on the right side that is in the backwashing position. The remaining filter elements 21 are in communication with the filter inlet 13 via the openings 35 in the filter support 31, such that fluid can flow into the internal cavity of these filter elements 21 for the filtration operation,

having the ability to reach the clean side, meaning the internal chamber 9 of the filter housing 1 from which point the filtrate is discharged by means of the filter outlet 15. A filter cover 39 is provided as a retaining means for the filter elements 21 that are located on the filter support 31, and said retaining means is screwed to the top end 41 of the drive shaft 27.

The storage unit that is configured as a piston accumulator 3 in the present embodiment is combined in the embodiment as shown here with the filter housing 1 to form a uniform structural unit. As shown in FIG. 2, the piston accumulator 3 is open at the bottom end 45 thereof that is seen at the bottom in the figure, and the cylinder jacket of the piston accumulator 3 crosses by the open end 45 thereof over the open end 11 of the top housing part 7 of the filter housing 1, to which it is screwed forming a seal. Correspondingly, the internal chamber 9 of the filter housing 1 constituting the clean side transitions virtually in a step-less manner into the cylinder chamber 43 of the piston accumulator 3 that forms the fluid side of the storage unit. The working chamber 49 of the piston accumulator 3 that is located on the opposite side of the piston 47 that serves as a movable separating element is closed except for a pressure means connection 51. As shown in FIG. 1, a valve means 53 is connected to the working chamber 49 via the pressure means connection 51. Using the valve means 53 it is possible to supply the working chamber 49 with an operating gas, as in the present example compressed air supplied by a compressed air line 55, or to lock the pressure means connections 51, or, as shown in FIG. 1, to connect the working chamber 49 via the connection 51 to the environment using a filter/choke means 57.

When the working chamber 49 is supplied during normal filtration operation with an operating gas (compressed air) that is adjusted to the system pressure of the filter device, it is possible for the piston accumulator 3 to act in the manner of a pulsation dampener. In this operational state, the backwashing line 59, which is connected to the backwashing outlet 19, is closed by a backwashing valve 61.

To start a backwashing process, the backwashing valve 61 is opened and the pressure means connection 51 of the piston accumulator 3 is connected to the compressed air line 55 by the valve means 53 in order to maintain the adjusted system pressure in the working chamber 49. Opening the backwashing valve 61 results in the discharge of a backwashing volume of fluid from the filter housing 1, which would, in fact, lead to a collapse of the volume flow of the filtered filtrate exiting from the outlet 15. Due to system pressure that is present in the working chamber 49 of the piston accumulator 3, the piston accumulator 3 therein provides a type of a push action acting as a pump in this situation that pushes a fluid volume out of the cylinder chamber 43 to the clean side 9 (internal chamber 9), whereby any drop in the volume flow of the fluid is avoided during the backwashing operation.

When the backwashing valve 61 is closed after backwashing is complete, the valve means 53 connects the working chamber 49 to the environment, such that compressed air escapes in a choked fashion via the means 57 (FIG. 1), until the piston 47 has moved a corresponding upward distance as in FIG. 2, and the volume of the cylinder chamber 43 has the desired value once again, such that, for any subsequent filtration operation with a closed valve means 53, there occurs a dampening of the pulsation once again, or a desired resupply volume is available for any subsequent backwashing process with compressed air supply to the working chamber 49.

In the depicted assembly, with a step-less transition of the filter housing 1 into the cylinder chamber 43 of the piston accumulator 3, there results, on the one hand, no loss due to flow resistance between the internal chamber 9 and cylinder chamber 43; moreover, on the other hand, a compact construction with a sufficiently large volume for embodying the chamber 43 and 49 of the piston accumulator is made possible, wherein the largest value of the volume of the cylinder chamber 43 constituting the fluid side can be substantially greater than the volume of the internal chamber 9 of the filter housing 1 surrounding the filter elements 21.

The pushing or pumping effect of the piston accumulator 3 during the backwashing process does not only prevent a collapse of the volume flow of the filtrate, but it is also beneficial for the efficiency of the filter cleaning operation during the backwashing process.

It is understood that other types of storage units can also be used in place of the envisioned piston accumulator 3, for example other hydro-pneumatic accumulators such as a bladder or diaphragm or bellows accumulator. Instead of the hydro-pneumatic accumulator, it is also possible to use means that provide for moving a separating element mechanically instead of pneumatically, for example by mechanically coupling an accumulator piston with a mechanical or electric or hydraulic drive, or by means of hydraulic pressure that acts upon the separating element.

Using the gas filling system of the accumulator, quick filling action of the gas chamber is made possible and, with the use of a correspondingly adaptable choke circuit, it is possible to slowly charge the accumulator to the pressure level in relation to the fluid of the filter unit. Moreover, the solution according to the invention is characterized in that the gas system or the gas filling system can be operated on a different pressure level than the level that is preset by the pressure level of the fluid filter in order to compensate for any pressure collapse of pressure fluctuations. Furthermore, the mentioned accumulator can be used in the manner of a dampener to smooth out pressure fluctuations in the system as a whole.

The use of correspondingly adapted wire mesh elements, instead of the aforementioned slotted screen tube elements 21, is also possible, and charging of the accumulator is optionally possible after a complete backwashing cycle, for example, involving all four elements or after backwashing only one element. 

1. A filter device comprising at least one filter housing (1) in which at least one filter element (21) is disposed that separates a clean side (9) from an untreated side (13) inside the filter housing (1), characterized in that at least one storage unit (3) having at least one movable separating element (47) is connected on the clean side (9) of the respective filter housing (1), which divides the storage unit (3) into two working chambers (49) or pressure chambers (43).
 2. The filter device according to claim 1, characterized in that the chamber of the storage unit (3), which is separated from the fluid chamber (43) that is connected to the clean side (9) of the filter housing (1) by the separating element (47), constitutes a working chamber (49) that can be connected to a source (55) for a pressure medium.
 3. The filter device according to claim 1, characterized in that a hydro-pneumatic pressure accumulator (3) is provided as a storage unit with a working chamber (49) that can be connected to a compressed air source (55).
 4. The filter device according to claim 1, characterized in that a pressure accumulator is provided in the form of a piston accumulator (3).
 5. The filter device according to claim 1, characterized in that the filter housing (1) forms a cylindrical internal chamber (9) with filter elements (21) in the form of filter cartridges being disposed in groups around the vertical axis (17) thereof and that allow for flow-through in both directions for filtration or backwashing, wherein at least one filter element (21) is backwashed by means of a backwashing means (373.59, 61) for cleaning the effective filter surface thereof while, simultaneously, the other filter elements (21) receive flow-through von the inside to the outside for the purpose of filtration, such that the internal chamber (9) of the filter housing (1) that surrounds the filter elements (21) constitutes the clean side that is connected to the fluid chamber (43) of the pressure accumulator (3).
 6. The filter device according to claim 1, characterized in that the internal chamber (9) is open at the top end (11) thereof and transitions into the cylinder chamber (43) constituting the fluid side of the piston accumulator (3) that is provided as pressure accumulator and that is coaxially disposed relative to the vertical axis (17) on the filter housing (1).
 7. The filter device according to claim 1, characterized in that the opening of the top end (11) of the internal chamber (9) of the filter housing (1) extends over the total inside diameter thereof, and in that the diameter of the cylinder chamber (43) of the piston accumulator (3) that follows immediately thereafter has at least the size of the diameter of the internal chamber (9) of the filter housing (1).
 8. The filter device according to claim 1, characterized in that the cylinder jacket of the piston accumulator (3) crosses over the top end (11) of the filter housing (1), is provided with an internal thread and screwed together with an external thread of the filter housing (1).
 9. The filter device according to claim 1, characterized in that the largest value of the volume of the fluid side (43) of the pressure accumulator (3) is equal to or greater than the volume of the internal chamber (9) of the filter housing (1) surrounding the filter elements (21).
 10. The filter device according to claim 1, characterized in that the backwashing means (37,59,61) includes a backwashing valve (61) inside a backwashing line (59) that is connected to the untreated side of the filter element (21) that is to be backwashed and which can be opened for the backwashing process, and in that a valve means (53) is connected to the working chamber (49) of the pressure accumulator (3) that can be triggered as a function of time and actuation of the backwashing valve (61) for supplying compressed air to or discharging compressed air from the working chamber (49) of the pressure accumulator (3).
 11. The filter device according to claim 1, characterized in that the filter elements (21) are disposed as pivotable around the vertical axis (17) and can be pivoted in sequence around said axis by means of a pivot means (23) that includes a rotary drive (25, 29) from the filtration position thereof into a backwashing position that is aligned with the backwashing line, and then pivoted around said vertical axis back into the filtration position.
 12. The filter device according to claim 1, characterized in that filter elements are tapered slotted screen tubes (21). 